This invention relates to bleach catalysts for use in cleaning or detergent compositions.
European laundry detergents usually contain oxygen-based bleaching agents such as sodium perborate or sodium percarbonate. These bleaches work well at temperatures above 60xc2x0 C., but to boost their overall effectiveness at today""s relatively low washing temperatures (e.g. 40-60xc2x0 C.), they are most commonly employed with so-called bleach activator compounds. The bleach activator, an example in commercial use of which is tetraacetylethylenediamine (TAED), is typically employed at a level of 3-6% in the detergent and reacts stoichiometrically with the persalt to yield a stronger oxidising agent, e.g. peracetic acid. This oxidant is better able to bleach stains than hydrogen peroxide and also has superior biocidal activity. However, as washing temperatures continue to decline, as a result of the demand for greater energy efficiency, even the commercially used activated bleach systems are becoming less attractive since their performance is known to decrease rapidly below 40xc2x0 C. Another drawback of these types of activator is their significant cost contribution to the detergent formulation, especially in proportion to that of the persalt component. Their rate of dissolution at low temperatures is also likely to reduce their effectiveness and may cause localised dye damage.
The development of interfacially active bleach activators, which react with persalts to produce peracids which are in turn interfacially active, has improved the performance of oxygen bleaches under certain conditions. The technology has meant that lower concentrations of the bleach system in the wash liquor are needed to give equivalent performance since the bleach is effectively targeted to the stains. Sodium nonanoyloxybenzene sulphonate (SNOBS) as described in U.S. Pat. No. 4,412,934, is an example of this type of activator. Although this disclosure has resulted in the successful introduction of perborate bleach-based detergents into the United States, where lower detergent concentrations are typically employed, it has done little to improve detergent performance at temperatures below 40xc2x0 C.
Much effort is being expended in the search for new organic bleach activators, however at present none has emerged which fulfils all the requirements, which must include (I) significantly improved bleach activity below 40xc2x0 C., (II) fast dissolving rate, (III) low cost, (IV) ease of processability into detergent formulations, (V) storage stability, (VI) compatibility with other detergent ingredients, and (VII) a non-toxic nature.
Another approach considered has been the use of pre-formed peracids as bleaches. An example of this is diperoxydodecanedioic acid (DPDDA). Although this, and other examples of pre-formed peracids, can lead to better bleaching performance than tetracetylethylenediamine (TAED) activated perborate, the peracids generally need stabilising coatings (as described for example in U.S. Pat. No. 4,100,095). Their use can also cause pin-hole damage to dyed fabrics.
Yet another approach taken within the detergents industry has been the use of bleach catalysts which work with oxygen bleaches such as sodium perborate or sodium percarbonate. EP-A-237,111 and EP-A-443,651 describe bleaching compositions comprising a water soluble complex of manganese with a multidentate ligand, such as hydroxycarboxylic acid and non-carboxylate polyhydroxy compounds respectively. EP-A-272,030 and EP-A-392,592 disclose Co(III)amine complexes (e.g. [Co(NH3)5Cl]Cl2) and Co(bispyridylamine)Cl2 complexes respectively, as effective catalysts for activating hydrogen peroxide compounds in removing stains from substrates, such as fabrics. Other patent specifications, for example WO 96/23859, WO 96/23860 and WO 96/23861, disclose cobalt catalysts such as [Co(NH3)5Cl]Cl2 and Co-SALEN type complexes to provide enhanced cleaning/bleaching benefits in automatic dishwashing detergents. Catalysts described by Rage et.al. in Nature 369, 637-639 (1994) and also in EP-A-458,397 and EP-A-458,398 are examples which give a considerable enhancement to persalt bleaching of stains on fabrics during washing at temperatures below 40xc2x0 C. However, these catalysts are prone to causing unacceptable dye and fabric damage due to the formation of radical catalyst decomposition products.
Another important characteristic of bleach catalysts is their hydrolytic stability. Lack of hydrolytic stability of the catalysts can result in precipitation out, under alkaline wash conditions, of insoluble transition metal oxides or hydroxides resulting in most undesirable brown staining. It is thus important that the complex employed as catalyst must have good hydrolytic activity on the one hand but still have good effectiveness as bleach catalysts on the other hand.
It has now surprisingly been found that water-soluble complexes of cobalt with aminated and/or alkylated mono- or oligo-saccharides, optionally in reduced or oxidised form, and salts thereof have high effectiveness as bleach catalysts and have high hydrolytic stability.
According to one aspect of the present invention, there is provided a water-soluble complex of (a) one or more cobalt ions and, as ligand, (b) one or more aminated and/or alkylated mono- or oligo-saccharides, optionally in reduced or oxidised form, and salts thereof for use as a bleach catalyst, in particular for a cleaning or detergent composition.
Suitably, in the complex used according to the present invention the cobalt ion(s) (a) is/are complexed with (b) one or more compounds of the general formula I 
wherein
R1 is selected from CH2OH, CO2H, CO2xe2x8ax96M⊕ (wherein M is an alkali metal or ammonium ion) and groups of the formula (a) to (d) 
xe2x80x83and n is an integer from 1 to 3;
one of R2 and R3 is H and the other is selected from H, OH and groups of the formula (e) to (h) 
xe2x80x83and m is an integer from 1 to 3;
one of R4 and R5 is H and the other is OH;
one of R6 and R7 is H and the other is OH or NH2; and
one of R8 and R9 is H and the other is OH, OCH2 (CH2)pCH3 (wherein p is an integer from 6 to 16), or a group of the formula 
xe2x80x83provided that one of R6 and R7 is NH2 and/or one of R8 and R9 is OCH2 (CH2)pCH3.
Also in the complex used according to the present invention, the cobalt ion(s) (a) may be complexed with (b) one or more compounds of the general formula II 
wherein
each of R10 and R11, which may be the same or different, represents H, CH2OH, CO2H or CO2xe2x8ax96M⊕ (wherein M is as defined above); and
each of l and k is an integer of 2 to 5 and k is equal to or less than l.
Preferably the cobalt ion(s) (a) is/are complexed with (b) D-mannosamine, D-glucosamine, or D-galactosamine, or with (b) one or more alkyl polyglucosides having a degree of polymerisation up to 5 and wherein the alkyl groups contain 8 to 18 carbon atoms.
Suitably the complex used according to the invention is a Co(II) or a Co(III) complex.
The complexes used according to the invention may be prepared by a method which comprises contacting in aqueous solution (A) a water-soluble compound capable of releasing Co(II) or Co(III) ions on addition to water with (B) one or more aminated and/or alkylated mono- or oligo-saccharides, optionally in reduced or oxidised form, and salts thereof.
For example, cobalt chloride hexahydrate (0.53 g) and mannosamine hydrochloride (24.1 g) were dissolved in 500 ml of demineralised water, the pH of the solution was adjusted to 10 using 1M sodium hydroxide solution and the solution was evaporated to dryness in a rotary evaporator.
The molar ratio of the ligand to cobalt may generally be between 1:1 and 500:1 with ratios in the region 50:1, e.g. 20:1 to 80:1 being particularly suitable.
According to another aspect of the present invention there is provided a cleaning or detergent composition comprising:
(I) a bleaching agent, and
(II) as bleach catalyst, a water-soluble complex as defined according to the present invention.
The cobalt bleach catalyst can, and indeed is preferably, formed in situ at the beginning of the wash cycle. Accordingly, according to a further aspect of the invention, there is provided a cleaning or detergent composition comprising:
(I) a bleaching agent, and,
as precursors for a bleach catalyst,
(IIA) a water-soluble compound capable of releasing Co(II) or Co(III) ions on addition to water, and
(IIB) one or more aminated and/or alkylated mono- or oligo-saccharides, optionally in reduced or oxidised forms, and salts thereof.
The water-soluble Co2+ or Co3+ compound (IIA) should be a compound which complexes preferentially with the compounds (IIB) in the composition. These compounds may be cobalt chloride or weakly complexed cobalt compounds.
The complexes used according to the invention promote bleaching activity and this is particularly noticeable at low temperatures (i.e. 20 to 40xc2x0 C.).
The bleaching agent (I) will generally be a peroxy compound which liberates hydrogen peroxide in water, preferably sodium perborate or sodium percarbonate.
The ligand component of the bleach catalyst (b) or precursor ingredient (IIB) may suitably be a cyclic ligand of formula I. Some of the ligands of formula I have surface active properties which provide further cleaning benefits towards oily and particulate solids in particular.
The ligand compounds used according to the invention are derived from starches or naturally occurring carbohydrates and thus are environmentally acceptable and toxicologically inert.
The compositions according to the invention may be laundry detergents or hard surface cleaners including automatic dishwashing detergents and may comprise other ingredients well known to those skilled in the art.
They may contain a bleach activator e.g. TAED.
The compositions according to the invention may contain a surfactant, for example, an anionic surfactant such as an alcohol sulphate or linear alkyl benzene sulphonate or non-ionic such as an alcohol ethoxylate.
In addition, the compositions according to the invention will generally contain builders such as alumino-silicates (e.g. zeolite A), layered silicates, phosphates particularly sodium tripolyphosphate, trisodium citrate, sodium carbonate or sodium borate.
Equally, there may be present polymeric additives such as maleic/acrylic copolymers which act as co-builders, and soil release polymers such as polyethylene oxide terephthalate.
The compositions according to the invention may also contain suds suppressors such as soap; enzymes such as lipase, amylase, cellulase and protease; optical brighteners such as stilbene derivatives; sequestrants or a combination of sequestrants with low affinity for cobalt but which will complex with other transition metals or if not, at a low enough level not to impair catalyst performance, and flow aids/fillers such as sodium sulphate.
Typically for detergent formulations according to the invention, assuming a typical usage level of detergent of 5 g/l (Europe), a suitable level of cobalt chloride hexahydrate and, for example, a mannosamine ligand in the detergent formulation would be in the order of 0.024 wt % and 1.08 wt % respectively.
In use the cobalt level may for example be in the range from 0.85 to 85 xcexcmoles Co/liter of wash liquor (0.05 to 5 ppm).
More detailed information on typical detergent compositions is disclosed in, for example, WO 92/06161.